1. Field of the Invention
The present invention relates to a valve housing which comprises a connecting part and a cap.
2. The Prior Art
Valve housings of this type are used, in particular, for valves and steam traps comprising an automatic compact control unit.
Known valve housings for valves and steam traps of this type comprise caps with a square flange as screw bearing. The caps are connected to the connecting part by four fastening screws (DE GM 1,948,583; U.S. Pat. No. 3,169,704; DE OS 2,059,798). This connection has been successfully used in practice. The fastening screws can be released without great expenditure of force for inspection or repair. No deforming stresses act on the pipe in which the valve housing is installed.
For connection to the pipe, the valve housings are equipped with different connecting ends, as required, for example welding sleeves (DE GM 1,948,583), screw-threaded sleeves (U.S. Pat. No. 3,169,704) or connecting flanges (DE OS 2,059,798). Known valve housings have a relatively small distance between the square flange for the cap and the connecting flanges. This applies, in particular, if the valve housings are constructed in the conventional standard lengths. The small distance between the connecting flange and the square flange is adequate to accommodate the screw nuts. However, the flange screws cannot be inserted into the screw holes in the connecting flanges from the valve housing side. Because of the respective local conditions, however, the flange screws cannot be inserted into the screw holes from the pipe side in each case.
As an alternative to the connection of the connecting part and the cap by means of fastening screws, a direct screw connection between the connecting part and the cap has been proposed for valve housings of automatic valves and steam traps (DE AS 1,115,065; DE PS 2,733,610). The square flange which obstructs insertion of the flange screws is unnecessary here. However, the threaded cap has only been used successfully in thermodynamic steam traps (DE PS 1,238,487). These steam traps have a very small diameter disc as the control element. The cap is also correspondingly small in size. On the other hand, temperature-sensitive control units are greater, despite having a compact construction. This also applies to the caps. A correspondingly great torque is required to tighten or release the thread of such a cap. This is associated with the risk of distortion of the attached pipe. Therefore, the threaded cap has not been successfully used on valve housings for valves and steam traps having control units of this type.